The present invention is directed to electromagnetic antennas, and especially to electromagnetic antennas employing a plurality of antenna elements known as patch antenna elements. Such patch antenna construction is advantageous in constructing antennas that are known as steerable beam antennas. Steerable beam antennas employ fixed antenna elements, such as patch antenna elements, to xe2x80x9csteerxe2x80x9d loci of sensitivity (i.e., transmitting beams or bearings of reception) by establishing predetermined interference patterns among the various patch antenna elements. The desired predetermined interference patterns are commonly effected by imposing phase differences among the various patch antenna elements.
One advantageous structure for imposing phase differences in electromagnetic signals delivered to or received by an antenna element has been disclosed in a pending patent application: application Ser. No. 09/838,483, filed Apr. 19, 2001, by Louise C. Sengupta and Andrey Kozyrev, for xe2x80x9cWAVEGUIDE-FINLINE TUNABLE PHASE SHIFTERxe2x80x9d, assigned to the assignee of the present invention.
It is desirable that steerable beam antennas be small and compact in construction in order that such devices may be used in inconspicuous applications. Closely or densely situating antenna patch elements used in such steerable beam antennas is desirable in order that maximum interaction among the various patch antenna elements may be realized. Electromagnetic signal coupling apparatuses associated with each respective antenna patch element have heretofore occupied a relatively large space and have mitigated against compact construction of arrays of antenna elements, such as antenna patch elements in a steerable beam antenna device. As a result, antenna patch elements have not been as densely situated as desired. One solution has been disclosed in the above-cited patent application: a waveguide-finline tunable phase shifter device. However, a waveguide structure (as disclosed in the above-cited patent application) still occupies a greater space than is desired in order that dense arranging of antenna patch elements in an antenna apparatus may be realized. Installing an antenna patch element that occupies a larger area is one solution that has been employed to provide a larger expanse in the vicinity of that patch element for effecting the requisite electromagnetic coupling and to accommodate a larger phase shifter structure. However, the larger the respective patch elements, the less resolution that can be established in steering beam operations. That is, larger patch elements yield coarser beam patterns that result in coarser control of beam steering operations.
There is a need for an apparatus for effecting tunable phase shifting of electromagnetic signals that permits closely arranged arrays of small antenna patch elements.
While such an apparatus is particularly useful for steerable beam antennas using closely arranged antenna patch elements, the apparatus has utility in other antenna coupling structures and arrangements. The invention disclosed, described and claimed herein is not limited to steerable beam antenna devices.
A tunable electromagnetic transmission structure for effecting coupling of electromagnetic signals having a frequency includes: (a) a dielectric substrate having an opposing first side and second side; (b) at least one first conductive land occupying a first area on the first side; (c) at least two second conductive lands on the second side separated by at least one substantially linear channel; the at least one channel having a width established by the frequency; the at least two second conductive lands and the at least one channel occupying a second area generally in register with the first area; and (d) a tunable dielectric material at least substantially filling the at least one channel; the tunable dielectric layer being electrically coupled with at least two second conductive lands of the at least two second conductive lands.
It is, therefore, an object of the present invention to provide an apparatus for effecting tunable phase shifting of electromagnetic signals that permits closely arranged arrays of small antenna patch elements.